Witches are a bit like Spies, anyone MIGHT be one but they should all be keeping it secret. I'd be really disappointed if we ended up with 'open' witchcraft, I don't feel the witches need to be artificially limited other then being a witch is incredibly dangerous. Even very powerful players should be hesitant to become a witch, it shouldn't be an automatic part of player progression, think of like becoming a Vampire, lots of power but huge downsides too.
Their should be something to push witches and non-witches apart, make them antagonistic towards each other, something that makes people genuinely angry at just having a witch live near them and makes them go for the pitch-forks and torches, a non-witch and a witch can never have a mutually beneficial relationship. Maybe witches passively drain all nearby non-witches inspiration, or bodily fluids, of some other nasty thing that makes you a really bad neighbor, only other witches would be immune.
Historically people believed that a person became a witch by signing their name in Satan's Book of the Damned. In other words it was the result of a pact that power was given too you, not the result of study/work/talent etc as Magic is often depicted. I propose we do something similar, but you the book you need to sign belongs to John Carver.
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